This invention relates to earthmovers, to excavators, and in particular to a hydraulically-actuated excavator of the front-loading, level-crowding variety.
The implement assembly of a front-loading hydraulic excavator, mounted on a full-revolving carrier of the trunk or wheel type, normally comprises a boom pivoted at one end on the vehicle, a stick pivotally connected at one end to the outer or front end of the boom, and a front-loading or front-opening bucket pivotally mounted on the other end of the stick. A hydraulic jack or jacks under operator control are provided for operation of each of the boom, the stick, and the bucket.
The excavator applies power to the bucket for cutting and the like solely through the manipulation of linkages, with the vehicle normally kept in a stationary position. This is in contrast to the usual loader machine wherein power is applied to the bucket for loading purposes by translation of the vehicle itself along the ground. In other words, power is applied to the excavator bucket by means of hydraulically operated linkages, whereas power is applied to the loader type bucket by means of the driving wheels of the vehicle.
Thus, the movement of the bucket in an excavator is controlled during its operation through the manipulation of the linkage system.
The application of power to the bucket by means of the linkage system requires careful and precise control of the linkage itself in order to achieve proper manipulation of the bucket. To achieve operations requiring a substantially level cut, all hydraulic jacks must be manipulated simultaneously by the operator. This requires diligence, experience and concentration by the operator. Such diligence and concentration hasten the fatique of the operator, resulting in his inefficient handling of this operation.
The prior art approach to bucket level control during crowding movement of the stick is disclosed in U.S. Pat. Nos. 3,862,697 and 3,927,781.